The invention relates to a device for turning sheets. Such devices are known, for example, in connection with letter sorting equipment. In this regard, the turning device serves to manipulate letters inserted in an arbitrary orientation, such that a side of preference in the transport system or in the pigeonholes at all times comes to lie on one specific side, such that the address of letters is visible and legible. The function of turning is discussed as follows. The letters to be turned are fed to a short, dead-end-like section of the transport system, are stopped there and accelerated again in reverse direction, thereby leaving the transport system in inverted manner. Due to the fact that the intervals between the letters in the transport system of the letter sorting apparatus are narrow and decelerating as well as accelerating take a long time, two turning devices must be arranged in parallel in the letter sorting apparatus in order to be able to continuously process the stream of letters. Moreover, the drive systems for decelerating and accelerating are relatively complex due to the masses of the transport elements involved. However, devices for turning sheets are known as well in connection with banknote sorting machines. For example, the banknotes to be turned can be clamped between two elastic flat belts guided across rollers in a manner arranged on top of each other and twisted by 180xc2x0. Such a device is shown also in EP 0 532 217 A1 for example. Although such a device permits continuous processing of the banknotes, the known device nevertheless entails the disadvantage that the banknotes, due to the twisting of the belts, are subject to mechanical loads during turning, whereby the banknotes may be damaged. Due to the system, there is moreover the disadvantage that only sheets arriving symmetrically can be passed on to the subsequent transport system in uniform manner. However, this constitutes considerably restricting marginal conditions in sorting banknotes, e.g. in singularizing, scanning and stacking.
U.S. Pat. No. 5,048,814 reveals a device for turning documents, which turns all of the documents fed to the device. To this end, there is provided a lever that is biased by the documents entering the device and presses the documents, after the same have fully entered the device, onto a belt running in the opposite direction. The documents then are transported out of the device in the opposite direction and thus are turned.
It is the object of the invention to suggest a device for turning sheets which, with low technical expenditure, renders possible continuous processing of the sheets, however, without subjecting the sheets to mechanical loads during turning.
This object is met by the features indicated in the main claim.
According to the invention, the sheets to be turned are fed into a gap between two transport elements continuously driven in opposite directions, with the particular sheet being pressed against the forward-moving or reverse-moving transport element by means of guiding elements actuated by an actuator. Preferably, the transport elements are in the form of elastic flat belts and the guiding elements are in the form of guide plates which, either with or without pressing rollers, press the sheet toward the one or other belt. Due to the low mass of the guide plates, e.g. a simple lifting magnet may be used as actuator, moving the guide plates in linear manner. Due to this, the switching times may be kept so short that, observing the minimum distance between two sheets, these can be processed in continuous manner. Additional advantages and further developments of the invention are set forth in the dependent claims as well as in the embodiments of the specification with reference to the drawings wherein